Abstract: The invention relates to a soundproofing bag (1) for single and double reed instruments, particularly for a saxophone made up of a material providing a fabric outer layer, an intermediate soundproofing layer, and an inner layer made up of air and steam permeable material, shaped in such a way to substantially conform to the shape of the instrument, and provided with a rear opening (9) allowing the hooking of the instrument, of a rear slot (13) for the hooking of the collar (5) to the saxophone, and with two entrances (10, 11), respectively for the introduction of the right and left hands to be able to normally play the saxophone.